I'm sure Mr. Stoddard will be along soon to bring this up, but his Locations: Worminghall has a monthly roll against "IQ + Magery" (IIRC, don't have book in front of me) to determine how effective teaching was. In the 8-month school year, it meant that gifted students could expect to gain around 4 skill points of spells per year. Not-so-gifted would probably gain around 3 (wild-a**ed-guess).

It should be noted Magery is effectively a talent for spells and thaumatology, without that reaction mod. But it does include the reduction in learning time.